For example, Patent Document 1 discloses a conventional vapor fuel processing apparatus equipped with a canister, which is configured to communicate with a fuel tank of a vehicle. The vapor fuel processing apparatus includes a tank sealing valve equipped at a path, which is configured to communicate the fuel tank with the canister. The tank sealing valve is configured to seal the fuel tank. The tank sealing valve is controlled at a closed state, excluding a part of a traveling condition of the vehicle or excluding when the vehicle is re-fueled. When re-fueling of the vehicle is detected, the tank sealing valve is maintained in an opened state until the re-fueling of the vehicle is completed. The tank sealing valve is opened, at the time point when the refueling of the vehicle is detected, thereby to enable to flow in-tank gas including fuel vapor into the canister, in advance of opening of the fueling port. The present operation is not to discharge fuel vapor from the tank to the atmosphere. In order not to discharge fuel vapor from the tank to the atmosphere, it is necessary to prohibit opening of the fueling port until in-tank pressure decreases sufficiently. Therefore, waiting time (de-pressurization waiting time) arises when the vehicle is refueled.
In addition, the in-tank pressure may become remarkably high, while the tank sealing valve is closed. In a case where the tank sealing valve is opened when the in-tank pressure is high, a large quantity of fuel vapor may flow from the fuel tank into the canister. In this case, the quantity of fuel vapor may be greater than a quantity of fuel vapor, by which the canister is capable of absorbing fuel vapor in a unit time. That is, a large quantity of fuel vapor, which exceeds an adsorption capacity of the canister per unit time, may flow from the fuel tank into the canister instantaneously. Therefore, it may be concerned that the canister may cause breakthrough to leak fuel vapor. Consequently, the leaking fuel vapor may flow through an atmospheric port of the canister into the atmosphere. In consideration of this, when the in-tank pressure is high, it may be desirable to reduce the flow quantity of fuel vapor in order to avoid leakage of fuel vapor from the atmospheric port of the canister to the atmosphere. Alternatively, when the in-tank pressure is low and when leakage of fuel vapor to the atmosphere is less possible, it may be desirable to flow a large flow quantity of fuel vapor in order to release pressure immediately.
It is assumable to employ a configuration of a flow control valve disclosed in, for example, Patent Document 2. Nevertheless, it is noted that, variation in inlet pressure may occur when the flow control valve is activated and when the flow control valve is returned.
(Patent Document 1)
Publication of unexamined Japanese patent application No. 2001-165003
(Patent Document 2)
Publication of unexamined Japanese patent application No. 2013-83296